Means for maintaining a suspension of ferromagnetic particles



Nov. 10, 1942. 2,301,203

mums FOR mmumme A SUSPENSION OF FERROMAGNETIC PARTICLES F. B. DQANE Filed Dec. 26, 1939 //r1z Ez-1Lz:7r faster flocme Patented Nov. 10, 1942 MEANS FOR MAINTAINING A SUSPENSION F FERROMAGNE'IIC PARTICEES Foster B. Doane, Wilmette, 111., asslgnor to Magnaflux Corporation, Chicago, 111., a corporation of Delaware Application December 26, 1939, Serial No, 310,949

9 Claims. (Cl. 259-95) It has heretofore been known that an object may be tested for flaws, cracks, discontinuities, and the like by subjecting the object to the influence of a magnetic field, while it is in contact with finely divided particles of magnetic material. These particles will indicate the'existence and degree of deviation of the lines of flux from their theoretical path and cause the particles to cling to the surface of the object at regions thereof where discontinuities or other defects exist, by reason of the magnetic polar effects exhibited by the object with their consequential leakage lines of flux.

In testing objects in this manner, considerable difllculty has heretofore been experienced in maintaining the finely divided particles of magnetic material in suspension in asuspensoid. The particles have a tendency to settle out of the suspensoid, particularly where a suspensoid of low viscosity or low specific gravity may be utilized in order to secure the necessary degree of mobility of the particles in the suspensoid medium.

, One of the characteristics of the materials now being utilized is that the longer it settles out,

i the harder it becomes and the more difficult it is to again get the material back into a satisfactory suspension. For this reason, the settling out of the particles is very undesirable and presents a difficult problem to be coped with during the testing operation by the foregoing described method.

Various arrangements have heretofore been suggested for keeping the suspensoid agitated; one of the principal arrangements being to provide a perforated pipe or pipes in a sump along the bottom of a tank for containing the suspensoid, and then forcing a circulation 'of the suspensoid through the pipe perforations into the testing tank. Such an arrangement has been found to be objectionable in that it becomes necessary to utilize an extremely violent agitation. This necessitates the use of greater power and a pump of larger size with the result that a greater undesirable heat dissipation occurs not only in the pump but of more importance in the suspensoid, and even though the most efficiently designed perforated pipes be utilized, it is still impossible to get an agitation capable of preventing dead spots.

With the above difficulties in mind, the present invention contemplates an improved means,

'whereby the particles in the suspensoid may be more readily and effectively maintained in suspension, and settling out of the particles prevented.

A further object of the invention is to provide a tank for the suspensoid which is of such shape that its walls may be kept clean and devoid of settled out particles by circulating and discharging the suspensoid into the tank in such direcin suspension, and utilizing these inclined surfaces to direct the movement of the particles to- .ward a point of concentration, and which utilizes circulated suspensoid for forcing the particles back into suspension before becoming concentrated.

Another object of the invention is to provide improved means in such apparatus for securing a double elongate narrow orifice in the tank'for the admission of suspensoid thereto in such direction that, any of the particles tending to settle out will be forced back into suspension, and including an improved arrangement for adjusting the orifice size.

Still another object is to provide an improved apparatus in which a tank is utilized for containing the suspensoid and particles in suspension therein; and in which a novel sump is pro- 'Vided from which suspensoid may be pumped and returned to the tank,.this sump containing a screen which is conveniently accesisble from the tank interior.

While the present invention is primarily adapted for use in connection with liquid suspensoid; it will be readily apparent to those skilled in the art that the apparatus may with equal facility be utilized with fluids as well as liquids, and the invention has been successfully utilized in connection with a gaseous medium containing dry powders in suspension.

Other objects and features of the invention will more fully appearfrom' the following detailed description taken in connection with the accompany ing drawing, which illustrates a single embodiment thereof, and in which:

Figure 1 is a view in elevation of apparatus embodying the features of the present invention, certain portions being cut away to disclose important details of construction; and I Figure 2 is an enlarged fragmentary transverse section through the same, taken substantially on line II--II of Figure 1-.

As shown on the drawing:

For purposes of illustration, the present invention is disclosed in the drawing as being embodied in one form of testing apparatus by means 'of which paramagnetic materials may be tested for defects by subjecting them to magnetizing forces while in the presence of ferromagnetic particles or other suitable particles held in suspension in a suspensoid.

The apparatus comprises an elongate tank or container III for the suspensoid, and has associated therewith a circulatory system by means of which the suspensoidmay be taken from the bottom adjacent the vertex thereof.

may be proportionally discharged either through a hose H5 or a conduit l'l communicating with the bottom of the tank.

As will be noted in Figure 1, the hose I6 is provided with a valve controlled nozzle l8 through which the suspensoid with the particles in suspension therein may be sprayed onto the object under test. The conduit H is preferably provided with a strainer I9 where it enters the tank.

As heretofore explained, the utilization of this type of testing equipment has met with considerable difficulty due to the settling out of the suspended particles and these particles becoming compacted into hard masses, on the tank surfaces and in other locations, which were not easily removable and which might interfere with the carrying out of the testing operation in an efllcacious manner, I

In order to overcome these objections and provide an arrangement for maintaining the particles in suspension, novel means have been pro- .vided as will now :be described.

In the present instance, the tank is constructed with opposed side walls -20 which are in downwardly converging relation to form a tank having a V shaped bottom construction. At the apex of the converged side walls, the bottom is reinforced by a longitudinally xtending angle-iron structural member 2|.

' members 22, each of these members being supported in inverted relation to the portion of the of the member or members 22', which are dis.- posed adjacent the tank endsfare closed by suitable means. In this instance an end plate 22' is welded or .otherwise secured to the legs of the angle member and is arranged to project below its. side'edges soas to also substantially close the subjacent portion in the V of the bottom. The side edges of the members 22 cooperate with the adjacent sides of the bottom respectively to cooperatively form spaced outlet orifices 2323 extending along the opposite sides of the bottom on either side of the vertex.

The members -22 are adjustably mounted on upstanding studs 24 which are threaded at their The ends Where a plurality of members 22 are utilized, these members are placed in end to end relation, and it is desirable that the abutting ends of the members be disposed adjacent the inlet [9 for suspensoid being pumped into the tank. Since the entering suspensoid will move outwardly from its point of admission with decreasing pressure as it approaches the remotely positioned ends of the members 22, it has been found desirable to have orifices of increasing size as the ends of the tank are approached, so as to more evenly regulate the distribution of the returned suspensoid along the tank length. This may be readily 8C.- complished by adjusting the thumb nuts associated with the respective members 22.

As more clearly shown in Figure 2, the action of the suspensoid being circulated through the orifices will now be described. It may first be I explained, however, that the tank. bottom portions tank side walls.

and the members 22 are so selected that their upwardly exposed surfaces will be angularly in-- clined at an angle greater 'than the angle of friction between the particlesin the suspensoid and the said surfaces. It may therefore be pointed out that as these particles tend to move downwardly in the tank and settle out due to the action of gravity thereon, the particles are intercepted in this movement by the inclined surfaces of the tank walls and the surfaces of the members.22, but the particles donot compact on these surfaces since their angle of inclination is greater than the angle of friction. The particles therefore move downwardly along these surfaces toward the respective orifices 23 or toward a position of concentration. Concentration of they particles is prevented, however, by the discharge of suspensoid through the orifices, this discharge being in such direction as to sweep the inner surfaces of the tank side walls and carry the particles back into suspension in the suspensoid. While in the present instance, the inclinationof these surfaces has been disclosed as it'is to be understood that different angles may be utilized fordifierent materials.

The arrangement described above is not only of simple construction, but the construction utilized is of such a nature that the path of discharge of suspensoid through the orifices may be readily varied by changing the angular disposition of the edge surfaces of the member 22 so as to give the optimum sweeping action Of'the discharged suspensoid over the inner surfaces of the The feature described above of being able to adjust the orifice opening permits the arrangement to be varied conveniently for various pump deliveries as well as variation in the delivery of a single pump over a period of time so as to get a the maximum velocity with any given pump.

Considerabl difiiculties have also been experienced in the arrangements heretofore, utilized in that the sump did not effectively prevent the settling out of the particles therein. The sump .in the present invention is so located and designed as to operate with very high efficiency and be quite free of and prevent the settling out of particles therein. The sump is located adjaa 7 2,301,208 through'the shell 21 is a strainer 28 which is -arranged to be inserted and removed from the shell through the tank interior. This provides an arrangement which enables the convenient removal of the strainer for cleaning the sam of foreign particles which might be trapped thereby. It is thought that the improved method for carrying out the present invention will be fully apparent without further description from the description of the apparatus herein.

From the foregoing description, it 'will be apparent that the present invention provides imi'orcing the particles back into suspension before becoming concentrated; which'utilizes improved means for obtaining a double elongate narrow orifice in the container for the suspensoid, including-novel means for adjusting th size of the orifices; and which utilizes an improved sump designed to prevent settling out of particles therein and in which a screen is conveniently accessible and arranged to permit removal thereof through the tank interior.

It will, of course, be understood that various details of construction may be varied through a wide range wihtout departing from the principles of this invention and itis, therefore, not the purpose to limit th patent granted hereon otherwise than necessitated by the scope and spirit of the appended claims.

I claim as my invention:

1. Apparatus for maintaining particles in suspension in a suspensoid comprising a tank having an inclined bottom, an elongate member having a tiltably mounted'edge cooperating with said bottom to define anadjustable elongate orifice, and means for circulating suspensoid from the tank and discharging it back into the tank below said member for passage through said orifice.

2. Apparatus for maintaining particles in suspension in a suspensoid comprising a tank having an inclined bottom, an elongate member having an edge cooperating with said bottom to define an elongate orifice, means for relatively moving said member and bottom for adiustingly varying said orifice, and means for circulating suspensoid through said orifice.

3. Apparatus for maintainingparticles in suspension in a suspensoid comprising a tank having an inclined bottom, an elongate member hav- 4. In apparatus of the character described, a

tank for a suspensoid, said tank having a laterally inclined bottom, a pair of elongate members disposed in end-to-end relation and cooperating with said bottom to form an' elongate orifice. means securing 'said members in positions inclined longitudinally upward from their adjacently disposed ends, whereby the orifice at said ends will be of diiferent size than at their remotely disposed ends, and means for discharging suspensoid into said tank at a point subjacent the adjacent ends of said members.

5. In apparatus of the character described, a container for a suspensoid having a transversely V shaped bottom, an elongate V shaped member 1 disposed in inverted position to form a false bottom for the container, said member being supported with its lateral edges respectively spaced from the bottom sides and cooperating therewith to form elongate orifices therealong, and means for supplying suspensoid to the container between said member and bottom.

6. In apparatus of the character described, a container for a suspensoid having a transversely V shaped bottom, an elongate V shapedmember I disposed in inverted position to form a false bottom for the container, said member being supported with its lateral edges respectively spaced from the bottom sides and cooperating therewith to form elongate orifices therealong, means for relatively moving the bottom and member to vary said orifices, and 'means for supplying suspensoid to the container between said member and bottom.

, 7. In apparatus of the character described, a container for a suspensoid having a transversely V shaped bottom, an elongate member forming a false bottom for the container, said member being supported with its lateral edges respectively spaced'from the bottom sides and cooperating therewith to form elongate orifices therealong, means biasing said member ionmovement away from said bottom, adjustable abutment means opposing said movement, and means for supplying suspensoid to the container between said member and bottom.

8. Apparatus adapted for producing a uniform suspension of solid particles tending to settle out in a liquid which comprises, a tank having convergent walls inclined at an angle greater than the angle of friction between the particles and said walls, whereby settling solids are directed to and concentrated at the convergence of said walls, means in said tank adiacent the convergence of said walls cooperating with the walls to define orifices on opposite sides of the means along the length oithe tank, and means for flowing liquid upwardly through said orifices to sweep any concentration of solids in the tank for forcing the settled solids back into suspension.

9. Apparatus adapted for producing a uniform suspension of particles in a liquid which comprises an elongated tank having inclined side walls converging to define a reduced bottom area in the tank, the degree of inclination of said side walls being greater than the angle of i'riction between said particles and said walls for guiding settling particles to a point of concentration at the reduced bottom area of the tank, an elongated member in said tank adjacent the reduced bottom area thereof and spaced from said side walls to cooperate therewith for definingnarrow orifices along the length of the tank, said member including top wail portions extending in downward directions to each orifice, and means for flowing suspending liquid from under said top wall portions of the member upwardly through said orifices to sweep settled particles back into I suspension.

FOSTER 2B. DOANE. 

